Feature Request: documentation of IAM permissions for LoginNodes

There does not seem to be minimal permissions for ec2/LoginNodes instance profile documented anywhere.
Probably want that botton down -- as it is becoming a main entry point for unprivileged users.

Start by locating the LoginNodes instance profile configuration and the existing AWS ParallelCluster IAM documentation. Identify the minimum permissions needed for LoginNodes and document them clearly; done means users can find an explicit least-privilege permission set for the instance profile.

Written by the indexing model from the issue text.